Unequal error protection for packet switched networks

ABSTRACT

A method of encoding at least two sets of data bits into a single encoded block is provided, wherein each set of data bits includes a primary set of bits to be encoded and a secondary set of bits to remain unencoded, wherein the encoding technique requires a set of code terminating bits to be added to the primary set of bits; the method comprising: combining the two sets of primary bits, whereby one set of code terminating bits is added to the combined two sets of primary bits. The two sets of data bits may each include a header portion and a payload portion, the payload portion comprising encoded speech. The encoding step may be a channel encoding step for encoding the at least two sets of data bits for transmission on a packet switched network. The data bits may be for transmission on an EDGE packet switched network, wherein the at least two sets of data bits are encoded into a single RLC/MAC block.

FIELD OF THE INVENTION

[0001] The present invention relates to encoding techniques for encodingmultiple sets of data for transmission, and particularly but notexclusively to the encoding of voice from more than one user in a singleRLC/MAC block for transmission on a packet switched network.

BACKGROUND TO THE INVENTION

[0002] Digital mobile communication systems for voice such as GSM(Global System for Mobile Communication), and DAMPS (Digital AdvancedMobile Systems) have expanded very rapidly in recent years.

[0003] In addition great demand for data service has been created bymobile users due to wide spread acceptance of the Internet. GPRS(General Packet Radio Service), EDGE (enhanced data rate for GSM), andUMTS (Universal Mobile Telecommunications Services) are all beingdeveloped to accommodate data users in wireless networks.

[0004] Schemes for the transmission of voice over fixed packet switchnetworks have also been developed in recent years and an increasingamount of voice traffic will be carried over packet switched networks inthe future.

[0005] The enhanced data rate for GSM evolution (EDGE) is a proposal forthe evolution of existing time division multiple access (TDMA) radiocellular systems in order to support higher transmission data rates andincrease the capacity of these networks. The application of EDGE isrestricted not only to GSM cellular networks but also has been acceptedfor the evolution of IS-136 systems by UWCC (Universal WirelessCommunications Consortium). Enhanced data rates are achieved byintroducing higher level modulation formats, such as 8-PSK (phase shiftkeying). With the introduction of such modulation schemes, EDGE systemscan offer bit rates of up to approximately three times higher thanstandard GSM/GPRS/IS-136 systems.

[0006] EDGE was initially developed in order to provide data service athigher rates than GSM or GPRS, by making use of multi-phase modulation(such as 8-PSK) instead of binary GMSK. However, the structure of theproposed RLC/MAC blocks for data transmission do not allow for theefficient use of the available radio resources for voice transmission.Furthermore, due to the use of 8-PSK more powerful channel coding isrequired in order to maintain certain levels of voice quality.

[0007] The use of more powerful channel encoding techniques generates alarger number of encoded bits. If the number of bits encoded exceeds thenumber of bit spaces available, then puncturing is usually applied toremove certain bits. A performance trade off therefore exists betweenproviding a powerful channel coding technique, but minimising the numberof bits to be punctured.

SUMMARY OF THE INVENTION

[0008] According to the present invention there is provided a method ofencoding at least two sets of data bits into a single encoded block,wherein each set of data bits includes a primary set of bits to beencoded and a secondary set of bits to remain unencoded, wherein theencoding technique requires a set of code terminating bits to be addedto the primary set of bits, the method comprising: combining the twosets of primary bits; and encoding the combined two sets of primarybits, whereby one set of code terminating bits is added to the combinedtwo sets of primary bits.

[0009] Preferred embodiments of the present invention advantageouslyprovide an improved encoding technique suitable for efficient channelencoding of voice on an EDGE network.

[0010] The two sets of data bits may each include a header portion and apayload portion, the payload portion comprising encoded speech. Theencoding step may be a channel encoding step for encoding the at leasttwo sets of data bits for transmission on a packet switched network. Thedata bits may be for transmission on an EDGE packet switched network,wherein the at least two sets of data bits are encoded into a singleRLC/MAC block.

[0011] According to the present invention there is also provided anencoder for encoding at least two sets of data bits into a singleencoded block, each set of data bits including a primary set of bits tobe encoded and a secondary set of bits to remain unencoded, wherein theencoding technique requires a set of code terminating bits to be addedto each primary set of bits, the encoder comprising: input means forreceiving the primary set of bits from each set of data bits andcombining them; encoding mans for encoding the combined primary set ofbits from each set of data bits; and output means for adding a singleset of code terminating bits to the combined encoded primary sets ofbits.

[0012] A packet switched network may include such an encoder.

[0013] The at least two sets of data bits may each include a headerportion and a payload portion, the payload portion including encodedspeech and the single encoded block being an RLC/MAC block.

[0014] The invention will now be described by way of example withreference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE FIGURES

[0015] FIGS. 1(a) and (b) illustrate a first example of a headerstructure for transmitting voice over an EDGE network;

[0016] FIGS. 2(a) and (b) illustrate a second example of a headerstructure for transmitting voice over an EDGE network;

[0017] FIGS. 3(a) and (b) illustrate a third example of a headerstructure for transmitting voice over an EDGE network;

[0018] FIGS. 4(a) and (b) illustrates system performance improvementsusing the header of FIG. 3;

[0019]FIG. 5 illustrates an encoder for generating the header of FIG.3(a);

[0020]FIG. 6 illustrates a decoder for decoding the header of FIG. 3(a);

[0021]FIG. 7 illustrates circuitry for generating an RLC/MAC block inthe down-link of an EDGE system;

[0022] FIGS. 8(a) to 8(c) illustrate one embodiment of the generation ofan RLC/MAC block from two speech frames from the same user in thedown-link of an EDGE network utilising the circuit of FIG. 7;

[0023] FIGS. 9(a) to 9(c) illustrate an embodiment, corresponding to theembodiment of FIG. 8, for generating an RLC/MAC block in the up-link ofan EDGE system;

[0024] FIGS. 10(a) to 10(e) illustrate one embodiment of the generationof an RLC/MAC block from four speech frames from different users in thedown-link of an EDGE network;

[0025] FIGS. 11(a) to 11(e) illustrate an embodiment, corresponding tothe embodiment of FIG. 10, for generating an RLC/MAC block in theup-link of an EDGE system;

[0026]FIG. 12 illustrates circuitry for generating an RLC/MAC block inthe down-link of an EDGE system;

[0027] FIGS. 13(a) to 13(c) illustrate one embodiment of the generationof an RLC/MAC block from two speech frames from different users in thedown-link of an EDGE network utilising the circuit of FIG. 12;

[0028] FIGS. 14(a) to 14(c) illustrate an embodiment, corresponding tothe embodiment of FIG. 13, for generating an RLC/MAC block in theup-link of an EDGE system;

[0029] FIGS. 15(a) to (d) illustrate conventional interleavingtechniques;

[0030]FIG. 16 illustrates a preferable interleaving technique for thedown-link of a wireless network;

[0031]FIG. 17 illustrates a preferable interleaving technique for theup-link of a wireless network;

[0032]FIG. 18 illustrates circuitry for generating an RLC/MAC block inthe down-link of an EDGE system;

[0033] FIGS. 19(a) to 19(c) illustrate one embodiment of the generationof an RLC/MAC block from two speech frames from the same users in thedown-link of an EDGE network utilising the circuit of FIG. 18;

[0034] FIGS. 20(a) to 20(c) illustrate an embodiment, corresponding tothe embodiment of FIG. 19, for generating an RLC/MAC block in theup-link of an EDGE system;

[0035]FIG. 21 illustrates a convnetional GSM/GPRS burst structure;

[0036]FIG. 22 illustrates one embodiment of a preferable burststructure;

[0037] FIGS. 23(a) to 23(c) illustrate an embodiment, corresponding tothe embodiment of FIG. 19, for generating an RLC/MAC block in theup-link of an EDGE system;

[0038]FIG. 24 illustrates another embodiment of a preferable burststructure; and

[0039]FIG. 25 illustrates an example implementation of the preferableburst structures of FIGS. 22 and 24.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0040] The enhanced data rate for GSM evolution (EDGE) has beendeveloped to support the transmission of data packets in wirelessnetworks. Networks supporting the transmission of data packets areconventionally known as packet switched networks. In packet switchednetworks such as EDGE, the data is transmitted in data packets whichinclude a header and a payload. Each data packet is encoded into a RadioLink Control/Medium Access Control (RLC/MAC) block. The payload includesthe information portion of the data packet. The header includes controland routing information associated with the data packet. For example,the header usually includes the destination address of the data packet,error checking information, and control bits for enabling receipt of thepacket to be acknowledged, and if necessary to request retransmission ofthe packet. One characteristic of data packet transmission is that ifthe receiver in the network does not successfully receive thetransmitted packet. then retransmission of the data packet is requested.

[0041] In sending voice, as opposed to data, the requirements fortransmission are different. For example, in voice transmission it isimpractical for information to be re-transmitted because of time delayconstraints. Therefore voice transmission in packet switched networks isunacknowledged voice packet transmission. In addition, with voicedifferent bits of the encoded speech have different importance, and itis acceptable for certain bits to be lost. However in data every bit isassumed to have equal importance, and no bits should therefore be lost.

[0042] It is herein proposed to transmit voice over an EDGE packetswitched network. In order to do this, a new RLC/MAC block structure isproposed in which the conventional EDGE header is modified to includethose fields required to support only voice transmission. Referring toFIG. 1, there is shown a first embodiment of a new RLC/MAC block header,suitable for transmission of voice over EDGE. The new RLC/MAC blockstructure includes a header which is reduced compared to the header ofthe data packets for EDGE. That is, the length of the header is shorterthan that which is required for the transmission of data packets.

[0043] Thus to send voice over an EDGE network, it is proposed to changethe RLC/MAC block of a standard data packet. The new block contains aheader, and a payload consisting of the coded speech bits coded using astandard GSM speech encoder.

[0044] This new RLC/MAC block is coded in a different way from that of aknown standard EDGE packet. This change of coding is required becausefor speech data different bits have different importance whereas fordata every bit has equal importance.

[0045]FIG. 1(a) shows a header for transmission of voice in thedown-link of an EDGE network. prior to channel encoding into an RLC/MACblock. The header 2 comprises an up-link status flag (USF) field 4, atemporary flow identity (TFI) field 6, and a final block indicator (FBI)field 8. The USF field is a 3 bit field, the TFI field is a 7 bit field,and the FBI field is a 1 bit field. All these fields, and there lengths,are defined by the GPRS standard which EDGE utilises, and thefunctionality of these fields in the reduced header is the same as inthe normal header used in EDGE for data packet transmission.

[0046]FIG. 1(b) shows a header for transmission of voice in the up-linkof an EDGE network. The header 10 comprises a temporary flow identity(TFI) field 12, a speech flag (SF) field 14, and a final block indicator(FBI) field 16. The TFI field is a 7 bit field, the SF field is a 2 bitfield, and the FBI field is a 1 bit field. The speech flag field isnewly introduced into an EDGE header, and corresponds to the S/P bit inGPRS.

[0047] In one preferable implementation of voice over EDGE as discussedhereinbelow, each EDGE RLC/MAC block contains two speech frames, andtherefore two speech flags are preferably provided in the up-link headerof FIG. 1(b), in order to signal whether each of these framescorresponds to silence or voice. The speech flag field may be increasedor reduced in dependence on whether more or less speech frames areincluded in the RLC/MAC block.

[0048] For completeness, a summary of each field of the up-link anddown-link headers of FIG. 1 is given hereinbelow, but one skilled in theart will be familiar with these fields and their functionality.

[0049] The USF field is used for unique addressing of the mobiles.Specifically, when a mobile receives a packet in the down-link, andreads the packets header and finds that it contains it's USF, this meansthat the base station has given permission to this mobile to transmitits packets on the up-link in a predefined timeslot.

[0050] The TFI field uniquely identifies a data flow. When a call isestablished, it is assigned a unique number. When a mobile station or abase station receives a packet and reads its header it knows which dataflow (call) this packet belongs to, by reading the TFI field.

[0051] When the SF field is set to 1, the speech frame corresponds tospeech. If the SF field is set to 0, the speech frame corresponds tosilence.

[0052] When the FBI field is set to 1, this is an indication to thereceiver that the current data flow is ended. If the FBI field is set to0, this means that there are more packets to be transmitted in thecurrent data flow.

[0053]FIG. 2 shows a second embodiment of the new header fortransmission of voice over EDGE. FIG. 2(a) shows the header fortransmission of voice in the up-link of an EDGE network further modifiedto include a set of error checking bits in a cyclic redundancy checking(CRC) field 18. The new header 20 still includes the USF field 4, theTFI field 6, and the FBI field 8.

[0054]FIG. 2(b) shows the header for transmission of voice in thedown-link of an EDGE network also further modified to include a set oferror checking bits in a cyclic redundancy checking (CRC) field 22. Thenew header 24 still includes the TFI field 12, the SF field 14, and theFBI field 16. The provision of the error checking bits provides extraprotection for the header. Although the headers of FIGS. 2(a) and 2(b)are described with reference to a CRC field for error checking, it willbe appreciated that any other error checking scheme suitable fordetection of errors may be utilised in accordance with the application.

[0055] The size of the CRC field in both the up-link and the down-linkheaders is dependent upon the error code used in the system. In a simpleerror checking scheme, the CRC field is generated in dependence upon theother fields in the header. At the receiver, the error field is comparedto a recalculation of the CRC field based on the received header, and ifan error is detected then the speech block is discarded. In datatransmission this is normal, and re-transmission of the data packet maybe requested after the original packet is discarded.

[0056] In voice, as mentioned hereinabove, re-transmission isimpractical. If voice is sent in packet switched networks then thestandard error techniques can result in a speech block being discardedon the basis of an error in the header alone, even when the speech inthe payload is error free.

[0057] Therefore there is proposed herein a further new header,generally applicable to any network in which information is sent in ablock comprising a header and a payload. This new header is describedherein with reference to a third embodiment of the header for voice overEDGE described with reference to other embodiments in FIG. 1 and FIG. 2,but it will be appreciated that the technique is in fact applicable toall packet switched networks. i.e. environments in which information isconveyed in packets or blocks having a header portion and a payload,whether the packet or block conveys speech or data.

[0058] The principle of this new header is to provide an error field inthe header which is generated in dependence only on bits contained inthe header. This error field is then used at the receiver end todetermine whether there are any errors present in the header. If one ormore errors are present in the header, then the nature of the errorfield is such that the receiver can attempt to correct the error orerrors introduced during transmission.

[0059] This means that blocks which are error free in the payload, orcontain acceptable errors, are not automatically discarded. Thereforesystem performance is increased, particularly for the transmission ofspeech in packet switched networks.

[0060] Referring to FIG. 3(a), the up-link header for transmitting voiceover EDGE is therefore modified still further to produce a new header 26in which the error checking field comprises a cyclic code scheme (CCS)field 28. Similarly referring to FIG. 3(b), the down-link header fortransmitting voice over EDGE has been modified still further to producea new header 30 in which the error checking field comprises a cycliccode scheme (CCS) field 32.

[0061] In the header 26 for the up-link for an EDGE network, a 15,10cyclic code is preferably used for protection of the header, having thefollowing generator polynomial:

g(D)=D ⁵ +D ⁴ +D ²+1

[0062] Thus a 15 bit header is generated from the original 9 bits of theheader. In accordance with the standard EDGE, the FBI bit is notincluded in the calculation of the CCS field. Such cyclic codes arewell-known, and within the scope of one skilled in the art. This blockcode has double-burst-error-correcting ability and single random errorcorrection capability. It can detect up to 3 random errors. It candetect all burst error patterns of length 5 or less. The fraction ofundetected error patterns of length equal to 6 is 0.0625. The fractionof undetected error patterns of length larger than 6 is 0.03125. Thecode has minimum distance of 4 and is the best code known with length 15and dimension 10.

[0063] In the header 30 for the down-link for an EDGE network a 15,9cyclic code is preferably used for protection of the header, and has thefollowing generator polynomial:

g(D)=D ⁶ +D ⁵ +D ⁴ +D ³+1

[0064] Thus a 15 bit header is generated from the original 10 bits ofthe header. In accordance with the standard EDGE, the FBI bit is againnot included in the calculation of the CCS field. This block code hasburst error correcting ability of three, and single random errorcorrection ability. It can detect up to 2 random errors. It can alsodetect all error patterns of length up to 6. The fraction of undetectederror patterns of length equal to 7 is 0.03125. The fraction ofundetected error patters of length 8 or higher is 0.015625. It is clearthat the TFI and SF fields are well protected and the error probabilityis significantly reduced with this code which has triple burst errorcorrecting ability.

[0065] Syndrome, which is the result of a calculation done at thereceiver upon reception of a code word, will be calculated for headerswithout error correction. If the syndrome value is zero, this is anindication that the code word contains no errors. The manner in whichthe syndrome is calculated depends upon the specific code used. The RLCblock will thus be accepted if the syndrome is right. If the syndrome iswrong. the header will be sent for error correction. The RLC block willbe discarded if the error corrector still indicates there are errors inthe header because the number of errors exceeds the code errorcorrection ability. When the error corrector indicates there are noerrors in the header after error correction, the RLC block will beaccepted and it assumes any errors in the header have been corrected.

[0066]FIG. 4 illustrates the simulation of performance results in thedown-link and the up-link, comparing the performance with and withouterror correction. In the simulation the system is assumed to beinterference free, and all results are presented as a function ofcarrier to interference ratio expressed in dB. Typical urban (TU)propagation conditions are assumed, and the mobile stations have a speedof 3 km/hr. Ideal frequency hopping is utilized. During thesesimulations the number of dropped headers when error detection is usedas well as the number of dropped headers when error correction is notused were calculated. In all cases a total number of 5000 RLC/MAC blocktransmissions have been simulated.

[0067] In both FIGS. 4(a) and 4(b) the performance table has fourcolumns. A first column 34 shows the carrier to interference ratio asdiscussed above, a second column 36 shows the number of dropped headerswithout error correction, a third column 38 shows the number of droppedheaders with error correction, and a fourth column 40 shows thepercentage improvement obtained by employing the new technique.

[0068] In FIG. 4(a), results for the down-link case where the 15,10cyclic code is utilized are shown. The relative percentage improvementarising from the use of error correction is also shown. FIG. 4(b) showscorresponding results for the case of up-link transmission where the15,9 cyclic code is utilized.

[0069] The headers with errors that have been corrected are betweenapproximately 10 to 20 percent according to the simulations. Because onecorrected header will save at least one speech frame, it will improvethe quality of speech significantly.

[0070] Referring to FIG. 5, there is shown a block diagram of an encodercircuit for generating a header for the down-link as shown in FIG. 3(a).The encoder circuit comprises a control circuit 50, a USF fieldgenerator circuit 52, a TFI field generator circuit 54, a FBI fieldgenerator circuit, a cyclic code generator circuit 58, and an outputcircuit 60. The control circuit 50 generates control and timing signalson lines 72 to each of the cyclic code generator circuit 58. and theheader field generator circuits 52, 54 and 56. The outputs of each ofthe USF and TFI header field generator circuits 52 and 54 on lines 74and 76 respectively form inputs to the cyclic code generator circuit 58.The cyclic code generator circuit generates the cyclic code from the 10bits of the respective fields of the header as discussed hereinabove,and generates the cyclic code on line 80, and the FBI field on line 78.The output circuit receives as an input the output of the cyclic codegenerator circuit on line 80. The output circuit then orders the signalson lines 74, 78 and 80 appropriately and generates the header of FIG.3(a) on line 68. Embodiments of the further encoding of the header aredescribed further hereinbelow.

[0071] It will be appreciated, from the block diagram of FIG. 5, how theencoder may be modified to provide an encoder for the up-link togenerate the header structure of FIG. 3(b).

[0072] Referring to FIG. 6, there is shown a block diagram of the partof the header decoding circuitry for error correction in the down-link.The part of the header decoding circuitry includes an input circuit 62,a cyclic code generator circuit 64, and an error correction anddetection block 66. The input circuit receives the 16 bits of thedecoded header, having the format of FIG. 3(a), on line 70. The fivebits of the cyclic code are provided on line 84 to the error correctionand detection block. The 12 bits of the header on which the cyclic codeis based are provided on line 82 to the cyclic code generator circuit,which applies the same cyclic code applied in the cyclic code generatorcircuit 58 of the transmitter. The thus generated additional cyclic codeis presented on line 86 to the error correction and detection circuit66. Thus the error correction and detection circuit 66 detects thepresence of an error and attempts to correct it as discussedhereinabove. Again, from the description hereinabove it can be readilyunderstood how the circuit of FIG. 6 can be modified for the up-link.

[0073] In the following discussion, specific examples of encoding speechframes for transmission over EDGE are given. In these example one oranother of the improved headers discussed hereinabove is utilised. Itwill be apparent, however, that alternative headers may be used whilststill gaining from the advantages of the described encoding techniques.

[0074] In transmitting voice over EDGE, it is advantageous whereverpossible to use the components of a standard speech encoder forgenerating the speech frames for transmission. In the followingexamples, standard GSM speech encoders are utilised. However, otherspeech encoders may be utilised. In GSM, speech frames have Class I bitsand Class II bits, and the Class I bits are further split into a ClassIa category and a Class Ib category. In general in speech different bitshave different importance, and therefore in a more general case theimportant bits (Class I in GSM) can be considered as primary bits, andthe less important bits (Class II in GSM) can be considered as secondarybits.

[0075] Two Speech Frames from Same User

[0076]FIG. 7 illustrates a block diagram of an encoder suitable forencoding two speech frames on the down-link of an EDGE system, when thetwo speech frames are associated with the same user. The encodercomprises a pair of preliminary coding circuits 104 and 106, a pair ofblock code circuits 112 and 118. a pair of reordering circuits 114 and120, a pair of convolution encoders 126 and 128, an output circuit 116,and a further block code circuit 140.

[0077] A standard GSM enhanced full-rate speech encoder generates aspeech frame having 244 bits. 174 of these bits are Class I bits, ofwhich 50 are Class Ia and 124 are Class Ib. The remaining 70 bits areClass II bits. The 244 bits of a first speech frame U1SF1 from a firstuser are received on a signal line 100, and the 244 bits of a secondspeech frame U1SF2 from the same first user are received on a signalline 102. Each of the 244 bit speech frames U1SF1 and U1SF2 are input toone of the respective preliminary coding circuits 104 and 106.

[0078] The preliminary coding circuits 104 and 106 each generate, on arespective output signal line 108 and 110, a set of 260 bits. Eachspeech frame U1SF1 and U1SF2 of 244 bits are passed through one of thepreliminary coding circuits to produce a respective set of 260 bits. Theadditional 16 bits are generated in the preliminary coding circuits byan 8-bit cycle redundancy code on the most important 65 bits of theClass I bits, and by two repetitions of the four most important Class IIbits. Thus each speech frame speech frame is modified to have 50 ClassIa bits, 132 Class Ib Bits, and 78 Class II bits, giving a total of 260bits. This preliminary coding step is in accordance with standard GSMtechniques.

[0079] The 50 Class Ia bits on the signal line 108 are input to theblock code circuit 112. Thereafter the 50 Class Ia bits are used togenerate 3 parity bits, such that 53 bits are generated on the outputline 121 of the block code circuit. Similarly the 50 Class Ia bits onthe signal line 110 are input to the block code circuit 118, whichgenerates 53 bits (including 3 parity bits) on line 124.

[0080] The 132 Class Ib bits on signal line 108 are input to thereordering circuit 114. The 132 Class Ib bits on signal line 110 areinput to the reordering block circuit 120. The 53 bits on signal line121 form a further input to the reordering circuit 114, and the 53 bitson signal line 124 form a further input to the reordering circuit 120.

[0081] Each of the respective re-ordering circuits 114 and 120additionally receive a set of six tail bits TB on the signal line 130and 132 respectively. A tail is then added to the end of the Class Ibits, in the reordering blocks 114 and 120 respectively, which are usedas trellis termination for the convolution encoder utilised for thefurther encoding of the Class I bits as discussed below. In EDGE sixtail bits are added.

[0082] The reordering circuit 114 reorders the 53 Class I bits on lines121, the 132 Class I bits on line 108, and the 6 tail bits on line 130to generate 191 Class I bits on signal line 122. The reordering circuit120 reorders the 53 Class I bits on lines 124, the 132 Class I bits online 110, and the 6 tail bits on line 132 to generate 191 Class I bitson signal line 125. The 191 bit outputs on lines 122 and 124respectively form inputs to the respective convolution encoder circuits126 and 128.

[0083] The 78 Class II bits on line 108 are input directly to the outputblock 116. The 78 Class II bits on line 110 are input directly to theoutput block 116.

[0084] Thus the 244 bit speech frames U1SF1 and U1SF2 are encoded, atthis stage, into respective 269 bit speech frames having 191 Class Ibits and 78 Class II bits.

[0085] The encoding of the speech frame up to now is in conformance withspeech encoding techniques used in GSM, and may be implemented in astandard GSM speech encoder. The one difference is that in standard GSMonly four tail bits are required. Therefore in standard GSM there areusually only 189 Class I bits at this stage.

[0086] In this advantageous embodiment of encoding two speech frames, anefficient coding technique is able to be utilised by encoding only oneheader, as opposed to two. That is, it is recognised that the headersassociated with the two speech frames are identical as they areassociated with the same user. Therefore, one header is discarded,resulting in a fewer number of bits needing to b encoded, as describedbelow As will also become apparent from the following description, therequirement for the encoding of only one header when the speech framesare generated using an enhanced full-rate encoder enables two speechframes to be encoded into a single RLC/MAC block without the need forany puncturing in the encoding, resulting in a very efficient codingscheme.

[0087] The 16 bits of the down-link header are presented on signal line138. In this example the advantageous header structure for the down-linkof FIG. 3(a) is utilised. The three USF bits form an input to the blockcode circuit 140, which generates 36 bits on its output signal line 142to the output circuit 116. utilising a standard block code from EDGE.The other 13 bits of the header on line 138 form a further input to theconvolution encoder circuit 126.

[0088] Referring to FIG. 8(a), there is shown the unencoded down-linkspeech block or packet described up to now. The 3 bits of the USF fieldof the header on line 138 are designated by numeral 150, the remaining13 bits of the header on line 138 are designated by reference numeral152. The 191 Class I bits of the first speech frame from the first useron line 122 are designated by reference numeral 154, and the 78 Class IIbits of the first speech frame from the first user on line 108 aredesignated by reference numeral 156. The 191 Class I bits of the secondspeech frame from the first user on line 124 are designated by referencenumeral 158, and the 78 Class II bits of the second speech frame fromthe first user on line 110 are designated by reference numeral 160.

[0089] As discussed hereinabove, the three USF bits of the down-linkheader are block coded into 36 bits and passed to the output circuit116, as designated by reference numeral 162 in FIG. 8(b). For theencoding of the USF field in the header the 36,3 linear block code assuggested for EDGE data transmission is used. The code is given below inTable I. TABLE I USF Encoded USF 000 000000000000000000000000000000000000 001 0000001110010111100100111011 10101111 0100001110010111100100111011101 01111000 011 000111110010101100001110011011010111 100 1110010111100100111011101011 11000000 1011110011001110011011111010000 01101111 110 111110010101100001110011011010111000 111 1111101011001111111000001101 00010111

[0090] The 191 Class I bits of the first speech frame on line 122 arecombined with the remaining 13 bits of the header (i.e. all fieldsexcept the 3 USF bits) on line 138 in the convolutional encoder circuit126. A 3,1,7 convolution code is utilised in the convolution encodercircuit 126 to generate 612 bits on the output signal line 134, whichare passed to the output circuit 116. These 612 bits are designated byreference numeral 164 in FIG. 8(b).

[0091] The 3, 1, 7 code utilised in this preferred embodiment is morepowerful than one proposed for data transmission in EDGE. The code has arate of ⅓ and a constraint length of 7 and therefore it is of the samecomplexity with the proposed for EDGE.

[0092] The generator polynomials of the rate 3, 1, 7 convolutional codeare as follows:

G ₀(D)=1+D ² +D ³ +D ⁵ +D ⁶

G ₁(D)=1+D+D ² +D ³ +D ⁴ +D ⁶

G ₂(D)=1+D+D ⁴ +D ⁶

[0093] This code is the best known code in its class. The free distanceof the code is d

=15. The code proposed in EDGE has a free distance of 14 (whenpuncturing is not applied).

[0094] The 78 Class II bits are passed to the output circuit 116unencoded from line 108. and are designated by reference numeral 166 inFIG. 8(b). It is standard in GSM for the Class II bits to be unencoded.

[0095] The 191 Class I bits of the second speech frame on line 125 areinput to the convolutional encoder circuit 128. The 3,1,7 convolutioncode is again utilised in the convolution encoder circuit 126 togenerate 573 bits on the output signal line 136, which are passed to theoutput circuit 116. These 573 bits are designated by reference numeral168 in FIG. 8(b).

[0096] The 78 Class II bits are passed to the output circuit 116 inunencoded form on line 110, and are designated by reference numeral 170in FIG. 8(b).

[0097] The output circuit 116 additionally receives 4 stealing bits SBon line 146. The four stealing bits are used to signal the type of theheader (as in data transmission over EDGE). Each TDMA burst contains onestealing bit. Four stealing bits are therefore provided, as it isproposed herein that the RLC/MAC block is spread over four bursts as fordata over EDGE. In addition to the 1377 bits generated and as shown inFIG. 8(b), this leaves the total number of bits as 11 short of thenumber of bits available in an EDGE RLC/MAC block. Thus the outputcircuit 116 additionally receives 11 spare bits SPB on line 148. Theoutput circuit then generates the completed EDGE RLC/MAC block on line149, comprising 1392 bits, for transmission.

[0098] Referring to FIG. 8(c), the completed RLC/MAC block for thedown-link is illustrated, and corresponds to the format shown in FIG.8(b) with the addition of the 4 stealing bits designated by referencenumeral 172, and the 11 spare bits designated by reference numeral 174.Reference numeral 176 represents the 1377 bits of FIG. 8(b).

[0099] In practice only one of the convolution encoders 126 or 128 maybe provided. Such a single convolution encoder may be utilised forencoding both speech frames in sequence.

[0100] Whilst the above description has been in relation to thetransmission of two speech frames in the same RLC/MAC block in thedown-link, and FIG. 8 represents a summary of the channel coding fortransmission of two speech frames in one RLC/MAC block for down-linktransmission, similar techniques apply in the up-link. FIG. 9illustrates the channel coding principle applied for transmission of twospeech frames in one RLC/MAC block for up-link transmission.

[0101] The encoder for generating the RLC/MAC block in the up-link willbe very similar to that in the down-link shown in FIG. 7, and istherefore not shown herein. The encoder in the up-link differs in thatthe block code circuit 140 for the header is not provided, and all 16bits of the up-link header of FIG. 3(b) are combined with the 191 bitson line 122 in the convolution encoder. In addition, the number of sparebits in the RLC/MAC block following convolution encoding is 38, andhence the number of spare bits SPB on line 148 is increased to 38.

[0102] Referring to FIG. 9(a), there is shown the unencoded up-linkspeech block or packet. The 16 bits of the header on line 138 aredesignated by reference numeral 180. The Class I bits of the firstspeech frame from the first user on line 122 are designated by referencenumeral 182, and the Class II bits of the first speech frame from thefirst user on line 108 are designated by reference numeral 184. TheClass I bits of the second speech frame from the first user on line 124are designated by reference numeral 186, and the Class II bits of thesecond speech frame from the first user on line 110 are designated byreference numeral 188.

[0103] The 191 Class I bits of the first speech frame on line 122 arecombined with 16 bits of the header on line 138 in the convolutionalencoder circuit 126. A 3,1.7 convolution code is again utilised in theconvolution encoder circuit 126 to generate 621 bits on the outputsignal line 134, which are passed to the output circuit 116. These 621bits are designated by reference numeral 190 in FIG. 9(b).

[0104] The 78 Class II bits are passed to the output circuit 116unencoded from line 108. and are designated by reference numeral 192 inFIG. 9(b).

[0105] The 191 Class I bits of the second speech frame on line 125 areinput to the convolutional encoder circuit 128. A 3,1,7 convolution codeis again utilised in the convolution encoder circuit 126 to generate 573bits on the output signal line 136, which are passed to the outputcircuit 116. These 573 bits are designated by reference numeral 194 inFIG. 9(b).

[0106] The 78 Class II bits are passed to the output circuit 116unencoded from line 110, and are designated by reference numeral 196 inFIG. 9(b).

[0107] Referring to FIG. 9(c), the completed RLC/MAC block for theup-link is illustrated, and corresponds to the format shown in FIG. 9(b)with the addition of the 4 stealing bits designated by reference numeral198, and the 38 spare bits designated by reference numeral 202.Reference numeral 200 represents the bits of FIG. 8(b).

[0108] On the up-link or the down-link the 1392 bits of the RLC/MACblock are passed to an 8-PSK modulator of the EDGE encoder. The RLC/MACspeech blocks are preferably interleaved over four bursts, as in thetransmission of data packets in EDGE.

[0109] At the receiver, the reverse decoding stages are utilised. If theheader of a received speech frame is in error, then an error correctionis attempted. If the error correction is successful, the received speechframe may still then be discarded if either of the two CRC checks is notsuccessful (the 3 bits protecting the 50 Class Ia bits or the 8 bits CRCprotecting the 65 most important Class I bits).

[0110] Thus in the above there has been described a technique forencoding two speech frames from the same user in a single RLC/MAC blockfor transmission over EDGE. Although this technique has beenspecifically described in relation to a technique for transmitting voiceover EDGE, it applies more broadly to the transmission of voice overpacket switched networks. The technique allows two speech frames fromone user to be encoded into a single RLC/MAC block using an encodingscheme which is proven to be advantageous. More importantly, there is norequirement for any puncturing of bits in implementing the encodingscheme. That is, there is no need to remove bits of the encoded speechframes to ensure that the number of bits fits into the RLC/MAC block, asmay normally be expected to be required with the encoding of speechdata. This particular advantage is achieved by utilising thecharacteristic that if two speech frames are from the same user, thenthe headers associated with those speech frames are identical. Thereforeone of the headers is redundant and can be removed from the packet to beencoded. This reduces the number of bits to be encoded and allows aparticularly advantageous coding scheme to be utilised.

[0111] In addition, it should be appreciated that this technique may beadvantageously utilised in encoding of more than two speech frames fromthe same user in a single RLC/MAC block. Regardless of the number ofspeech frames, if they are from the same user only one header isrequired.

[0112] In the following description, two examples are given of theencoding of two speech frames which are associated with different users.One characteristic of speech frames from different users is that in thedown-link one user does not have any information about the other user.

[0113] The principle described hereinabove for encoding four speechframes from the same user in a single RLC/MAC block may be furtherextended to the encoding of larger numbers of speech frames from thesame user in a single RLC/MAC block.

[0114] Two Speech Frames from Different User—Case 1

[0115] Referring to FIG. 12, there is shown a block diagram illustratingone embodiment for encoding two speech frames from two different usersin the down-link of a packet switched network. The down-link encoder ofFIG. 12 corresponds substantially to the down-link encoder of FIG. 7,and like reference numerals have been used to denote like elements. Themain difference lies in the addition of a further block code circuit141. In addition the convolution encoder circuits 126 and 128 aremodified to additionally include puncturing, as will be describedfurther hereinbelow.

[0116] This embodiment utilises the 244 bit speech frames generated byan enhanced full-rate GSM speech encoder, as described hereinabove withreference to FIG. 7. The 244 bits of a first speech frame U1SF1 from afirst user are received on the signal line 100, and the 244 bits of afirst speech frame U2SF1 from a second user are received on the signalline 102. Each of the 244 bit speech frames U1SF1 and U2SF1 areprocessed by the preliminary coding circuits 104 and 106, the block codecircuits 112 and 118, and the reordering circuits 120 exactly asdescribed hereinabove with reference to FIG. 7.

[0117] As the two speech frames are from different users, then there aretwo respective different headers associated with each speech frame.Hence the block code circuit 141 is introduced to handle the headerassociated with the second user speech frame on line 102. The headerassociated with the first user speech frame on line 100 is processed inthe same manner as the common header is processed in the circuit of FIG.7, by the block code circuit 140.

[0118] The 16 bits of the down-link header for the second userassociated with the speech frame U2SF1 are presented on signal line 139.The three USF bits form an input to the block code circuit 141, whichgenerates 36 bits on its output signal line 143 to the output circuit116, utilising the standard block code from EDGE discussed hereinabovewith reference to FIG. 7. The other 13 bits of the header on line 139form a further input to the convolution encoder circuit 128.

[0119] Referring to FIG. 13(a), there is shown the unencoded down-linkspeech block or packet, including two speech frames from two differentusers, prior to the operation of the convolutional encoder circuits withpuncturing 126 and 128. In this example, each speech frameadvantageously utilises the header format of FIG. 3(a). A first speechframe from a first user thus includes a USF field 212 of the header 213,and the remainder of the header is designated by reference numeral 214.The Class I bits of the first speech frame from the first user aredesignated by reference numeral 216, and the Class II bits from thefirst speech frame from the first user are designated by referencenumeral 218. A first speech frame from a second user includes a USFfield 220 of the header 221, and the remainder of the header isdesignated by reference numeral 222. The Class I bits of the firstspeech frame from the second user are designated by reference numeral224, and the Class II bits from the first speech frame from the seconduser are designated by reference numeral 226.

[0120] As discussed above, the 3 bits of the USF field 212 of the headerassociated with the first user are block encoded in the block codecircuit 140 to give 3 bits on line 142, designated by reference numeral238 in FIG. 13(b).

[0121] The 191 Class I bits of the first speech frame from the firstuser on line 122 are combined with 16 bits of the header on line 138 inthe convolutional encoder circuit with puncturing 126. A 3,1,7convolution code is again utilised in the convolution encoder circuit126, and the encoder circuit punctures 34 bits such that 578 bits aregenerated on the output 134 of the encoder circuit. These 578 bits aredesignated by reference numeral 230 in FIG. 13(b).

[0122] In a preferable implementation, the puncturing scheme used is asfollows:

b(9+j*17) j=0, 1 . . . 33,

[0123] where b(i) is the output of the 3,1,7 encoder. This scheme willnot puncture any CRC bits. For Class I bits, the total output is 573bits, with the CRC bits located in positions 151 to 159. The closestbits to the CRC which are punctured are bits 145 and 162. The last bitpunctured is 570.

[0124] The 78 Class II bits 218 are passed to the output circuit 116unencoded from line 108, and are designated by reference numeral 232 inFIG. 13(b).

[0125] As discussed above, the 3 bits of the USF field 220 of the headerassociated with the second user are block encoded in the block codecircuit 141 to give 3 bits on line 143, designated by reference numeral240 in FIG. 13(b).

[0126] The 191 Class I bits of the first speech frame from the seconduser on line 125 are input to the convolutional encoder circuit 128. A3,1,7 convolution code is again utilised in the convolution encodercircuit 128, and the encoder circuit punctures 34 bits such that 578bits are generated on the output 136 of the encoder circuit 128. These578 bits are designated by reference numeral 234 in FIG. 13(b).

[0127] The 78 Class II bits 224 are passed to the output circuit 116 inunencoded form on line 110, and are designated by reference numeral 236in FIG. 13(b).

[0128] The encoder of FIG. 12 also differs from that of FIG. 7 in thatthere are 8 stealing bits SB provided on line 146, and there is norequirement for spare bits to be provided.

[0129] Referring to FIG. 13(c), the completed RLC/MAC block for thedown-link is illustrated, and corresponds to the format shown in FIG.13(b) with the addition of the 8 stealing bits designated by referencenumeral 240. Reference numeral 242 represents the bits of FIG. 13(b).

[0130] Four more stealing bits are added to guarantee a complete in-bandsignal when the second user is absent.

[0131] On the up-link or the down-link the 1392 bits of the RLC/MACblock are passed to an 8-PSK modulator of the EDGE encoder. The RLC/MACspeech blocks are preferably interleaved over four bursts, as in thetransmission of data packets in EDGE.

[0132] At the receiver, the reverse decoding stages are utilised. If theheader of a received speech frame is in error, then an error correctionis attempted. If the error correction is successful, the received speechframe may still then be discarded if either of the two CRC checks is notsuccessful (the 3 bits protecting the 50 Class Ia bits or the 8 bits CRCprotecting the 65 most important Class I bits).

[0133] The encoder for generating the RLC/MAC block in the up-link willbe very similar to that in the down-link shown in FIG. 12, and istherefore not shown herein. The encoder in the up-link differs in thatit is effectively simply half of the encoder shown in FIG. 12. Theoperation of the encoder in the up-link is best illustrated withreference to FIG. 14

[0134] In the up-link, each user encodes its associated speech frame.Thus FIG. 14(a) illustrates the unencoded speech frame for one of theusers, for example the first user. Again, the preferable header formatof FIG. 3(b) is used in the up-link. The unencoded speech frame. asshown in FIG. 14(a), comprises a header field 256 comprising the 16 bitsof FIG. 12, the 191 Class I bits designated by reference numeral 258,and the 78 Class II bits designated by reference numeral 260.

[0135] In the up-link, the full 16 bits of the header are convolutionencoded with the Class I bits, as discussed hereinabove in theembodiment of two speech frames from the same user. Again, the 3,1,7convolution code is used, and in the case of the up-link it is necessaryto puncture 7 bits. Thus in the up-link the convolution encodergenerates 614 bits 262 as shown in FIG. 14(b). In the up-link only 7bits are punctured.

[0136] The puncturing scheme used in a preferable implementation is forClass Ib bits only, and may be expressed as:

b(200+j*49) j=0, 1 . . . 6,

[0137] where b(i) is the output of the 3,1 encoder. This scheme will notpuncture any CRC bits. The CRC bits are located at 151 to 159.Puncturing starts at 200 and finishes at 494.

[0138] The 78 Class II bits are included in the encoded speech frame 252unencoded as before, and are designated by reference numeral 264.

[0139] The thus encoded speech frame 252 has four stealing bits 266added thereto, and this represents half of an RLC/MAC block as shown inFIG. 14(c), where the bits of FIG. 14(b) are represented by referencenumeral 268.

[0140] Interleaving Scheme

[0141] The present description has a particular emphasis on theapplication of techniques to an EDGE system. In EDGE, it is proposedthat data packet encoded into an RLC/MAC block should be transmitted onthe down-link or the up-link in four bursts. That is the 1392 bits of anRLC/MAC block should be split into four sections, with each sectionbeing sent in a separate burst.

[0142] As will be familiar to one skilled in the art, each burstoccupies a time slot of a TDMA frame. That is, transmission in a TDMAsystem takes place in a series of TDMA frames, each of which is splitinto a number of time slots. Each time slot, in a circuit switchednetwork having dedicated physical channels, is allocated to, andreserved for sole use by, one particular user. Each user then transmitsin their time-slot of each TDMA frame, both in the down-link and theup-link.

[0143] Referring to FIG. 15(b), there is shown the standard format of aGSM/GPRS burst. The burst 600 comprises a set of 3 tail bits 606 at thefront. followed by a set of 58 data bits 608, followed by a set of 26bits 610 comprising a training sequence, followed by a set of 58 databits 612, followed by a further 3 tail bits 614 and finally a set of8.25 bits comprising a guard 616.

[0144] Information is transmitted on the physical channel in TDMA timeslots, as illustrated in FIG. 15(a). In a TDMA system each TDMA timeframe 611 comprises a set of time slots, and in the example of FIG.15(a) each time frame comprises a set of eight time slots TN1 to TN8.Each time slot TN1 to TN8 of a TDMA frame carries a burst having theformat shown in FIG. 15(b). Ordinarily, each time slot within a frame isreserved for use by a particular user.

[0145] Referring to FIG. 15(c), the interleaving of a data RLC/MAC blockinto TDMA frames in a conventional GSM/GPRS system is shown. Block 800represents the 464 bits of a first RLC/MAC speech block associated witha first user, block 802 represents the 464 bits of a second RLC/MACblock associated with the same first user, and block 804 represents the464 bits of a third RLC/MAC speech block associated with the same user.

[0146] In conventional GSM/GPRS, the 464 bits of a particular block,e.g. the second block 802, are interleaved over eight bursts (in eightTDMA frames) with the least half of the bits from the previous block 800(designated by reference numeral 801) and the first half of the bitsfrom the next block 804 (designated by reference numeral 805).

[0147] Thus, as indicated by the arrows in FIG. 15(c) and as is wellunderstood by one skilled in the art, the first set of 58 bits(including the stealing bits) of the block 802 are interleaved in thethird time slot of a first time frame TF1 with the fifth set of 58 bitsof the block 800. The second set of 58 bits of the block 802 areinterleaved in the third time slot of a second time frame TF2 with thesixth set of 58 bits of the block 800. The third set of 58 bits of theblock 802 are interleaved in the third time slot of a third time frameTF3 with the seventh set of 58 bits of the block 800. The fourth set of58 bits of the block 802 are interleaved in the third time slot of afourth time frame TF4 with the eighth set of 58 bits of the block 800.The fifth set of 58 bits of the block 802 are interleaved in the thirdtime slot of a fifth time frame TF5 with the first set of 58 bits of theblock 804. The sixth set of 58 bits of the block 802 are interleaved inthe third time slot of a sixth time frame TF6 with the second set of 58bits of the block 804. The seventh set of 58 bits of the block 802 areinterleaved in the third time slot of a seventh time frame TF7 with thethird set of 58 bits of the block 804. The eighth set of 58 bits of theblock 802 are interleaved in the third time slot of an eighth time frameTF8 with the fourth set of 58 bits of the block 804. The sets of bitsare selected to minimise correlation.

[0148] Conversely in the EDGE proposal, each RLC/MAC block istransmitted over four time frames, and hence over four time slots infour successive time frames as illustrated in FIG. 15(d).

[0149]FIG. 15(d) represents the arrangement of EDGE when an 8 PSKmodulator is used. This allows each conventional burst to accommodatethree times the conventional number of bits, i.e. 464 (456 bits pluseight stealing bits). Thus the 1392 bits of an EDGE RLC/LAC block,represented by block 810 in FIG. 15(d), are interleaved over foursuccessive TDMA time frames TF1 to TF4 in the third time slot. Each timeslot carries a single burst carrying 348 bits of data.

[0150] As can be seen from FIG. 15(d), each burst can carry 348 bits ofdata, and therefore the 1392 bits of data of the encoded RLC/MAC blockcan be transmitted over four bursts. However, in the embodimentsdescribed herein for the transmission of voice over EDGE the 1392 bitsof data may be from two different users, and ordinarily each user wouldneed to be allocated a separate time slot in each time frame.

[0151] In order to facilitate a particularly advantageous transmissionscheme, there is proposed herein a scheme in which two users share atime slot within a TDMA frame on both the down-link and the up-link.This scheme may be applied advantageously to the transmission of speechframes from two different users over EDGE encoded according to thetechnique described hereinabove.

[0152] According to the new technique proposed herein, the data fromeach of the two users is transmitted in a common time frame. Referringto FIG. 13(c) it can be seen that the encoded RLC/MAC block comprises696 bits associated with the first user (including four stealing bits),and 696 bits associated with the second user (including four stealingbits). In accordance with the new technique, in the down-link a quarterof the encoded bits associated with the first user are transmitted in anallocated time slot of each frame on four successive frames, and aquarter of the encoded bits associated with the second user aretransmitted in the same allocated time slot of each time frame on thesame four successive frames.

[0153] Thus, suppose that time slot TN3 is allocated to the two users.In time slot TN3 of time frame TF1 174 bits (including one stealing bit)of the encoded RLC/MAC associated with the first user are transmitted inthe data portion 608 of the burst, and 174 bits (including one stealingbit) of the encoded RLC/MAC associated with the second user aretransmitted in the data portion 612 of the burst. In time slot TN3 oftime frame TF2 a further 174 bits (including one stealing bit) of theencoded RLC/MAC associated with the first user are transmitted in thedata portion 608 of the burst, and a further 174 bits (including onestealing bit) of the encoded RLC/MAC associated with the second user aretransmitted in the data portion 612 of the burst. This is then repeatedfor a further two bursts such that all 1392 bits of the burst aretransmitted in four successive bursts.

[0154] Referring to FIG. 16, there is further illustrated the principleof such a scheme applied to the down-link, for transmitting the RLC/MACblocks of FIG. 13(c).

[0155] A block designated by reference numeral 400 represents 160samples of speech associated with a first user in a 20 ms time frame,prior to initial channel encoding. As represented by the arrow 404,these 160 samples are encoded into a 260 bit speech frame for the firstuser as designated by reference numeral 408, which are the set of bitson the output 108 of the preliminary coding circuit 104. These 260 bitsstill occupy a 20 ms time period. The 260 bits of the speech frame arethen encoded into the 696 bits constituting half of the RLC/MAC block onthe output 149 of the output circuit 116, which step is represented byarrow 412. The 696 bits of the RLC/MAC block are designated by referencenumeral 416.

[0156] Similarly, for the second user, the arrows 406, 410 and 414correspond directly to the functions illustrated by the arrows 400, 408and 416 respectively. The blocks designated 402, 410, and 414 for thesecond user correspond directly to the blocks 404, 412 and 416 for thefirst user.

[0157] Thus the block 418 corresponds to the set of 696 bits of theRLC/MAC block of FIG. 13(c) associated with the second user.

[0158] The third time slot of the TDMA frames is allocated to bothusers. In a first frame TF1 a first quarter of the encoded data for eachuser plus two respective steering bits is transmitted. In a second frameTF2 a second quarter of the encoded data for each user plus tworespective stealing bits is transmitted. In a third frame TF3 a thirdquarter of the encoded data for each user plus two respective stealingbits is transmitted. In a fourth frame TF4 a fourth quarter of theencoded data for each user plus two respective steering bits istransmitted. Thus the whole RLC/MAC block is transmitted over fourbursts or time slots.

[0159] In a preferred implementation, the coded bits are reordered andinterleaved according to the following rule:

i(B,j)=c(n,k)

[0160] for:

[0161] k=0, 1, . . . , 691

[0162] n=0, 1, . . . , N, N+1, . . . where n is the frame number.

[0163] The result of the interleaving is a distribution of the reordered692 bits of a given user one speech block, n=N, over 4 blocks using theeven numbered bits of the first 2 blocks (B=B0+2N+0,1) and the oddnumbered bits of the last 2 blocks (B=B0+2N+2, 3). The reordered bits ofthe second user speech block, n=K, use the odd numbered bits of thefirst 2 blocks (B=B0+2N+0, 1) and the even numbered bits of the last 2blocks (B=B0+2N+2, 3).

[0164] The mapping is given by the rule:

[0165] e(B.j)=i(B,j) and e(B, 176+j)=i(B, 174+j) for j=0, 1, . . . , 173

[0166] and

[0167] e(B,174)=SB(2B) and e(B,175)=SB(2B+1)

[0168] The two bits, labeled SB(2B) and SB(2B+1) on burst number B areflags used for indication of control channel signaling.

[0169] In the up-link, the technique proposed with reference to FIG. 16is not feasible, since neither user is synchronised with the other.However an adaptation of the technique is still possible, which stillemploys the concept of the two users sharing the same time slot totransmit the 1392 bits of the RLC/MAC block over four successive bursts.

[0170] Again, suppose that time slot TN3 is allocated to the two users.In time slot TN3 of time frame TF1 174 bits (including one stealing bit)of the encoded RLC/MAC associated with the first user are transmitted inthe data portion 608 of the burst, and a further 174 bits (including onestealing bit) of the encoded RLC/MAC associated with the first user aretransmitted in the data portion 612 of the burst. In time slot T3 oftime frame TF2 174 bits (including one stealing bits) of the encodedRLC/MAC associated with the second user are transmitted in the dataportion 608 of the burst, and a further 174 bits (including one stealingbit) of the encoded RLC/MAC associated with the second user aretransmitted in the data portion 612 of the burst. The remaining bitsassociated with the first user are then transmitted in the third timeframe TF3, and the remaining bits associated with the second user arethen transmitted in the fourth time frame.

[0171] Referring to FIG. 17, there is further illustrated the principleof such a scheme applied to the up-link, for transmitting the RLC/MACblocks of FIG. 13(c).

[0172] The blocks 400, 408, and 416 in FIG. 17 correspond to the sameblocks as like reference numerals in FIG. 16, and are associated withthe first user. The blocks 402, 410, and 418 in FIG. 17 similarly referto the same blocks as like reference numerals in FIG. 16, and areassociated with the second user.

[0173] The 696 bits of the RLC/MAC block for the first user aredesignated by reference numeral 416, and the 696 bits of the RLC/MACblock for the second user are designated by reference numeral 418.

[0174] Similarly, for the second user, the arrows 406, 410 and 414correspond directly to the functions illustrated by the arrows 400, 408and 416 respectively. The blocks designated 402, 410, and 414 for thesecond user correspond directly to the blocks 404, 412 and 416 for thefirst user.

[0175] The 696 bits of the encoded RLC/MAC block are interleaved overtwo even/odd bursts and passed to the 8-PSK modulator.

[0176] In the up-link, the coded bits are preferably reordered andinterleaved according to the following rule:

[0177] i(B,j)=c(n,k) for k=0, 1, . . . , 691

[0178] n=0, 1, . . . m N, N+1, . . .

[0179] The result of the interleaving is a distribution of the reordered692 bits of the user one speech block, n=N, over 2 even blocks(B=B0+2N+0, 2) and the reordered bits of the user two speech block, n=K,use odd blocks (B=B0+2N+1, 3).

[0180] The mapping is given by the rule:

[0181] e(B,j)=i(B,j) and e(B, 176+j)=i(B, 174+j) for j=0, 1, . . . , 173

[0182] and

[0183] e(B.174)=SB(2B) and e(B,175)=SB(2B+1)

[0184] The two bits, labeled SB(2B) and SB(2B+1) on burst number B areflags used for indication of control channel signaling.

[0185] Two Speech Frames from Different User—Case II Referring to FIG.18, there is shown a block diagram illustrating a second embodiment forencoding two speech frames from two different users in the down-link ofa packet switched network. The down-link encoder of FIG. 18 correspondssubstantially to the down-link encoder of FIG. 12, and like referencenumerals have been used to denote like elements. The main differencelies in the combining of the convolution encoder circuits withpuncturing 126 and 128 into a single convolution encoder circuit withpuncturing 127.

[0186] In this embodiment, the header for the down-link shown in FIG.1(a) is used.

[0187] The 244 bits of the first speech frame U1SF1 from the first userare received on the signal line 100, and the 244 bits of the firstspeech frame U2SF1 from the second user are received on the signal line102. Each of the 244 bit speech frames U1SF1 and U2SF1 are processed bythe preliminary coding circuits 104 and 106, and the block code circuits112 and 118 exactly as described hereinabove with reference to FIGS. 7and 12.

[0188] The reordering circuit 120 processes the 53 Class Ia bits on line124 and the 132 Class II bits on line 110 in exactly the same manner asdescribed hereinabove with reference to FIGS. 7 and 12. Thus thereordering circuit 120 generates the reordered 191 bits, including the 6tail bits supplied on the tail bit input TB on line 130.

[0189] The reordering circuit 114, however, is modified relative to there-ordering circuit 114 of FIGS. 7 and 12. The reordering circuit 114 ofFIG. 18 does not receive any tail bits, and thus the 185 bits at itsinput are presented on its output line 122. The reason why the tail bitsare not provided to the reordering block 114 are most easily understoodwith reference to FIG. 19.

[0190]FIG. 19(a) illustrates the format of the two speech frames, andtheir associated headers, prior to encoding into the format for theRLC/MAC block.

[0191] The 3 bits of the USF field from the first user's header on line138 are designated by reference numeral 282. The 3 bits of the USF fieldfrom the second user's header on line 139 are designated by referencenumeral 284. The remaining 8 bits of the first user's header on line 138are designated by reference numeral 286, and the remaining 8 bits of thesecond user's header on line 138 are designated by reference numeral288. The 185 Class I bits from the first user on line 122 are designatedby reference numeral 290, and the 191 Class I bits from the second useron line 125 are designated by reference numeral 292. The 78 Class IIbits from the first user on line 108 are designated by reference numeral294, and the 78 Class II bits from the second user on line 110 aredesignated by reference numeral 296.

[0192] It can be seen from studying FIG. 19(a), and comparing it to FIG.13(a), that the fields in the unencoded block of FIG. 19(a) have beenrearranged such that equivalent fields from each user are adjacent. Thisintroduces an advantage by the location of the two Class I fields ofeach block adjacent each other. As discussed hereinabove, the six tailbits are introduced into the Class I bits as a tail to terminate theconvolution encoder. By placing the two sets of Class I bits together,and encoding them together, the set of tail bits for one set of Class Ibits can be removed. Thus the set of tail bits associated with the firstuser is eliminated, and hence the reordering circuit 114 only needs togenerate 185 bits, and does not need to include any tail bits.

[0193] This saving of bits results in the more efficient implementationof the convolution code. The combined convolution encoder circuit withpuncturing encodes the two remaining sets of 8 bits of each header andthe two sets of Class I bits into a set of 1112 bits by utilising the3,1,7 convolution code as discussed above. The convolution encoder withpuncturing punctures 16 bits. The encoded speech frames are illustratedin FIG. 19(b). The 1112 convolution encoded bits are designated byreference numeral 300.

[0194] The puncturing scheme is applied for Class Ib bits only and thepreferable scheme is represented by:

[0195] b(200+j*49) j=0, 1 . . . 7, where b(i) is the output of the 3,1,7encoder.

[0196] b(755+j*49) j=8, . . . 15, where b(i) is the output of the 3,1,7encoder.

[0197] The total number of bits reduces from 1128 to 1112.

[0198] As described before with reference to FIG. 12, each of the 3 bitUSF fields are encoded in the block code circuits 140 and 141 into arespective set of 36 bits, using the block code described hereinabove.The 36 bits corresponding to the first user are designated by referencenumeral 302 and the 36 bits corresponding to the second user aredesignated by reference numeral 304.

[0199] Each set of 78 Class II bits are unencoded as before, and aredesignated by the reference numerals 306 and 308.

[0200] Referring to FIG. 19(c), there is shown the final encoded RLC/MACblock 310, which comprises the 1388 bits from FIG. 19(b) designated byreference numeral 312, together with 4 stealing bits designated byreference numeral 314.

[0201] The down-link, in this embodiment, utilises the interleavingtechnique introduced in FIG. 16 for interleaving the RLC/MAC blocks ontofour bursts.

[0202] For this particular embodiment, there are two alternativetechniques discussed hereinbelow for encoding on the up-link. Asdiscussed hereinabove for the first embodiment of two speech frames fromdifferent users on the up-link, neither user has any information aboutthe other, and therefore each speech frame from each user is encodedseparately.

[0203]FIG. 20 shows a first example of up-link coding. In FIG. 20(a)there is shown an unencoded speech block 322 having a header designatedby reference numeral 326 corresponding to that of FIG. 1(b), a set of191 Class I bits designated by reference numeral 328, and a set of 78Class II bits designated by reference numeral 330.

[0204] The encoded speech block 322 is illustrated in FIG. 20(b). Inthis example, the up-link header and the set of Class I bits are encodedtogether by a 2,1,7 convolution code, with puncturing of 28 bits.

[0205] The preferable puncturing scheme applied for Class Ib bits onlyis: b(110+j*10) j=0, 1 . . . 27, where b(i) is the output of the ½encoder. The total number of bits reduces from 402 to 374.

[0206] This results in a set of 374 bits as designated by referencenumeral 332. As before the 78 Class II bits remain unencoded, and aredesignated by reference numeral 334.

[0207] Finally, the RLC/MAC block 324 for transmission is illustrated inFIG. 20(c), and includes all the bits of FIG. 20(b) designated byreference numeral 336 together with the 4 stealing bits designated byreference numeral 328.

[0208] The speech frame of the second user is similarly encoded, andresults in an RLC/MAC block with the identical format to that of FIG.20(c).

[0209] New Burst Structure

[0210]FIG. 21 illustrates the conventional structure of a normal burst,and is identical to that shown and described previously with referenceto FIG. 15(b). However, in FIG. 21 the number of bits in each portion ofthe burst corresponds to those which can be accommodated using 8 PSKmodulation.

[0211] In the following a new burst structure based on the GSM/GPRSburst structure is proposed, which advantageously utilises the encodingtechnique for the up-link described with reference to FIG. 20. Referringto FIG. 22 there is shown a new burst structure 602, equivalent inlength to the burst structure of FIG. 21. but having tail portions 618,626, 630 and 638, data portions 620, 624, 632, and 636, trainingsequences 622 and 634, and guard portions 628 and 640. The 456 bits ofan encoded RLC/MAC block are interleaved over four half bursts andpassed to the 8 PSK modulator.

[0212]FIG. 23 shows a second example of up-link coding. In FIG. 23(a)there is shown the unencoded speech block 320 of FIG. 20(a).

[0213] The encoded speech block 340 is illustrated in FIG. 23(b). Inthis example, the up-link header and the set of Class I bits are encodedtogether by a 3,1,7 convolution code, with puncturing of 181 bits.

[0214] This scheme uses (3,1,7) convolutional code rather than (2,1,7)convolutional code in previous section. This code has better coding gainbut it produces more bits and lot puncturing has to be done.

[0215] Puncturing schemes are used:

[0216] b(43+j*3) j=0, 1 . . . 44, where b(i) is the output of the ⅓encoder.

[0217] b(193+j*3) j=0, 1 . . . 135, where b(i) is the output of the ⅓encoder.

[0218] This scheme will not puncture any header or CRC bits. The headeris located at bits 1 to 30 and the CRC is located at bits 181 to 189.

[0219] This results in a set of 422 bits as designated by referencenumeral 342. As before the 78 Class II bits remain unencoded, and aredesignated by reference numeral 344.

[0220] Finally, the RLC/MAC block 350 for transmission is illustrated inFIG. 23(c), and includes all the bits of FIG. 23(b) designated byreference numeral 348 together with the 4 stealing bits designated byreference numeral 346.

[0221] The speech frame of the second user is similarly encoded, andresults in an RLC/MAC block with the identical format to that of FIG.23(c).

[0222] Referring to FIG. 24 there is shown a further adaptation of thenew burst structure 604 of FIG. 22, again equivalent in length to theburst structure of FIG. 21, but having tail portions 642, 650, 652 and660, data portions 644, 648, 654, and 658, and training sequences 646and 656. Thus the new burst structure of FIG. 24 corresponds to the newburst structure of FIG. 22, but without any guard bands. The 504 bits ofthe encoded RLC/MAC block in FIG. 23 are interleaved over four halfbursts and passed to the 8 PSK modulator.

[0223] Referring to FIG. 25, there is illustrated an example of theencoding technique described above with reference to FIG. 20, and theinterleaving of the encoded RLC/MAC blocks into the new burst structure.The blocks 400, 408, and 416 in FIG. 25 correspond to the same blocks aslike reference numerals in FIG. 17, and are associated with the firstuser. The blocks 402, 410, and 418 in FIG. 25 similarly refer to thesame blocks as like reference numerals in FIG. 17, and are associatedwith the second user. In this example each of the blocks 416 and 418comprises 456 bits corresponding to the 456 bits of FIG. 20(c) for eachof the first and second users.

[0224] As illustrated in FIG. 25, each time frame includes a time-slot,which is assumed to be the third time slot TN3, which is partitionedinto two time slots. Thus in a first time frame TF1 the third time slot900 is divided into a first sub-time-slot 908 and a second sub-time-slot910. In a second time frame TF2 the third time slot 902 is divided intoa first sub-time-slot 912 and a second sub-time-slot 914. In a thirdtime frame TF3 the third time slot 904 is divided into a firstsub-time-slot 916 and a second sub-time-slot 918. In a fourth time frameTF4 the third time slot 906 is divided into a first sub-time-slot 920and a second sub-time-slot 922. The other time-slots of each time frameare not shown for reasons of clarity in the Figure.

[0225] Thus, in accordance with this technique, a quarter of the 456bits associated with the first user and represented by block 416 aretransmitted in each of the four sub-time-slots 908, 912, 916, and 920. Aquarter of the 456 bits associated with the second user and representedby block 418 are transmitted in each of the four sub-time-slots 910,914, 918, and 922. The burst structure in each sub-time-slot correspondsto that of FIG. 22.

[0226] In this way each physical channel formed by a conventional timeslot becomes two physical channels. In this way an eight physicalchannel system may become a sixteen physical channel system.

[0227] Thus the original burst can be treated as two separate bursts.The information of a first user will occupy the first new burst (the tophalf of the original burst), and the information of the second user willoccupy the second new burst (the bottom half of the original burst).Interleaving may be done by the conventional GSM/GPRS method, but with anew size of 456 for the burst structure of FIG. 22, and a new size of504 for the burst structure in FIG. 24.

[0228] The partitioning of each time slot into a greater number ofsub-time-slots is possible. Thus, in general, if a time slot normallysupports a burst structure having n bits, each time slot may bepartitioned into m sub-time-slots, bits being transmitted in eachsub-time-slot in a corresponding burst structure having n/m bits.

[0229] In the general case, data from p users may be encoded such thateach forms 1/p bits of an RLC/MAC block, wherein the encoded data isencoded into one of a p sub-time-slots.

[0230] Using the coding technique of FIG. 20, the burst structure ofFIG. 24 may be similarly utilised in a system such as FIG. 24. The guardband of the structure of FIG. 22 may be eliminated where there is goodsynchronisation between the users.

[0231] Thus in a circuit or packet switched TDMA network, the number ofphysical channels may be doubled or further increased.

[0232] The interleaving technique for transmitting user data fromdifferent users in the same time slot, described hereinabove withreference to, for example, FIGS. 16 and 17 may be combined with thetechnique described hereinabove with reference to, for example, FIG. 25,for partitioning a time-slot. In this way sub-time-slots may bepartitioned.

[0233] Four Speech Frames from Different Users

[0234] A further embodiment is now described in which four speech framesall associated with different users are encoded into a single RLC/MACblock for transmission over EDGE. In this embodiment a standard GSMHalf-rate encoder is utilised.

[0235] A standard GSM half-rate speech encoder generates a speech framehaving 112 bits. 95 of these bits are Class I bits, of which 22 areClass Ia and 73 are Class Ib. The remaining 17 bits are Class II bits.

[0236] The ordering of the bits of a half-rate speech frame is shown inFIG. 10(a).

[0237] As can be seen, the speech frame 700 comprises the 73 Class Ibbits 702, followed by the 22 Class Ia bits 704, and followed by the 17Class II bits 706.

[0238] In standard GSM, the Class Ia bits of the half-rate encodedspeech frame 700 of FIG. 10(a) are protected by three parity bits usedfor error detection. After addition of the three parity bits, a 115 bithalf-rate encoded speech frame 708 is formed having the format shown inFIG. 10(b). The three parity bits 710 are positioned between the ClassIa bits 704 and the Class II bits 706.

[0239] The circuitry for generating the half-rate encoded speech frame708 of FIG. 10(b) may be a standard GSM speech encoder, theimplementation of which will be well within the scope of one skilled inthe art. The circuitry for further encoding such speech frames into anEDGE RLC/MAC block will also be apparent to one skilled in the arthaving reference to the circuit of FIG. 7 described hereinabove and thefollowing additional description. For reasons of conciseness, a furthermodified implementation of such a circuit is not shown here. Thenecessary modifications to the circuit of FIG. 7 will be apparent fromthe following description with further reference to FIGS. 10 and 11.

[0240] The encoding of the half-rate speech frame up to now is inconformance with speech encoding used in GSM. In this example theadvantageous header structure for the down-link of FIG. 3(a) is againutilised.

[0241] Referring to FIG. 10(b), there is shown one unencoded down-linkspeech frame 712 associated with one user. The 3 bits of the USF fieldof the header on line 138 are designated by numeral 720, the remaining13 bits of the header are designated by reference numeral 722.

[0242] The three USF bits of the down-link header are block coded into36 bits as designated by reference numeral 726 in FIG. 10(d). For theencoding of the USF field in the header the 36,3 linear block code assuggested for EDGE data transmission and shown hereinabove in Table I isused.

[0243] The 95 Class I bits 702 and 704 of the first speech frame arecombined with the remaining 13 bits of the header 722 (i.e. all fieldsexcept the 3 USF bits) and the 3 CRC bits 710 in a convolutional encodercircuit. A 3,1,7 convolutional code is utilised as described above togenerate 351 bits designated by reference numeral 724 in FIG. 10(c).

[0244] The 3,1,7 convolutional code described hereinabove with referenceto FIG. 7 is again used, having the generator polynomials of the rate3,1,7 convolutional code as follows:

G ₀(D)=1+D ² +D ³ +D ⁵ +D ⁶

G ₁(D)=1+D+D ² +D ³ +D ⁴ +D ⁶

G ₂(D)=1+D+D ⁴ +D ⁶

[0245] The output of the convolutional encoder comprises 351 bits [b(1),. . . , b(351)]. In order to fulfil the length requirements of the EDGERLC/MAC block, puncturing must be used at this stage. More specifically,58 of the 351 bits 724 are punctured to result in a set of 293 encodedbits designated by reference numeral 728 in FIG. 10(d). The puncturedbits are the following:

[0246] b(40+5.1)=0, i=0, 1, . . . , 56

[0247] b(324)=0

[0248] Careful examination of the punctured bits shows that none of thecritical CRC and header bits are punctured.

[0249] The 17 Class II bits are unencoded and are designated byreference numeral 730 in FIG. 10(d).

[0250] Referring to FIG. 10(e), the completed RLC/MAC block 742 for thedown-link is illustrated, and corresponds to the format shown in FIG.10(d) with the addition of 8 stealing bits designated by referencenumeral 734 and encoded second, third, and fourth speech framesdesignated 736, 738, and 740.

[0251] Each of the second, third, and fourth half-encoded speech framesfrom the same user are encoded in an identical manner to that describedin relation to the first speech frame with reference to FIGS. 10(a) to10(d). In this embodiment all speech frames are encoded with theirheaders-, since with the technique used—puncturing 58 bits perframe—this results in a length of bits (with the 8 stealing bits)equivalent in length to an EDGE RLC/MAC block.

[0252] At the receiver end, prior to decoding, the punctured bits arereplaced with zeros. The punctured block consists of 293 bits, which arecombined with the 36 encoded USF bits and the 17 uncoded Class II bitsto form the first block of the transmitted RLC/MAC block. The sameprocedure is followed for the rest three speech frames. At the end 8stealing bits are inserted. After the RLC/MAC block is formed, it isforwarded to the modulator and interleaver. Interleaving over fourbursts is preferably used in the downlink as in EDGE data transmission.

[0253] Because all the headers are encoded, this same technique may beused for encoding four speech frames which are not all associated withthe same user.

[0254] Whilst the above description has been in relation to thetransmission of four speech frames in the same RLC/MAC block in thedown-link, and FIG. 8 represents a summary of the channel coding fortransmission of four speech frames in one RLC/MAC block for down-linktransmission, similar techniques apply in the up-link. FIG. 11illustrates the channel coding principle applied for transmission offour speech frames in one RLC/MAC block for up-link transmission.

[0255] Referring to FIG. 11(b), there is again shown one unencodeddown-link speech frame 713 associated with one user. The 16 bit headeris designated by numeral 723.

[0256] The 95 Class I bits 702 and 704 of the first speech frame arecombined with the 16 bits of the header 723 and the 3 CRC bits 710 in aconvolutional encoder circuit. A 3,1,7 convolution code is againutilised to generate 360 bits (including 6 tail bits) designated byreference numeral 750 in FIG. 11(c).

[0257] The output of the convolutional encoder comprises 360 bits [b(1),. . . , b(360)]. In order to fulfil the length requirements of the EDGERLC/MAC block, puncturing must again be used at this stage. 31 of the360 bits 750 are punctured to result in a set of 329 encoded bitsdesignated by reference numeral 756 in FIG. 10(d). The punctured bitsare the following:

[0258] b(53+9·i)=0, i=0, 1, . . . 29

[0259] b(324)=0

[0260] The 17 Class II bits 706 are unencoded. The encoded frame 752 isthen allocated two stealing bits 766 and multiplexed into an RLC/MACblock with the three other frames. Each of the three other encodedframes 760, 762, and 764 is associated with two stealing bits 768, 770,and 772 respectively.

[0261] As will be discussed later herein, if four encoded speech framesare from different users, in a preferable embodiment they may share acommon TDMA time slot.

[0262] Each encoded frame is preferably transmitted in one burst. Sincefour different blocks may come from four different users in the uplink,it is not possible to interleave the RLC/MAC block over four bursts.Alternatively block interleaving is used for each block in each burst.Specifically, the 346 bits are inserted in a 18×20 rectangular matrixcolumn by column. This matrix has 360 elements and therefore the last 14elements are empty. The bits are read out row by row. This interleavingscheme achieves a minimum distance of 18 between consecutive bits. Atthe receiver end the inverse procedure (de-interleaving) is followed.

1. A method of encoding at least two sets of data bits into a singleencoded block, wherein each set of data bits includes a primary set ofbits to be encoded and a secondary set of bits to remain unencoded,wherein the encoding technique requires a set of code terminating bitsto be added to the primary set of bits, the method comprising: combiningthe two sets of primary bits; and encoding the combined two sets ofprimary bits, whereby one set of code terminating bits is added to thecombined two sets of primary bits.
 2. The method of claim 1, wherein thetwo sets of data bits each include a header portion and a payloadportion, the payload portion comprising encoded speech.
 3. The method ofclaim 1 or claim 2 wherein the encoding step is a channel encoding stepfor encoding the at least two sets of data bits for transmission on apacket switched network.
 4. The method of claim 3 wherein the data bitsare for transmission on an EDGE packet switched network, wherein the atleast two sets of data bits are encoded into a single RLC/MAC block. 5.An encoder for encoding at least two sets of data bits into a singleencoded block, each set of data bits including a primary set of bits tobe encoded and a secondary set of bits to remain unencoded, wherein theencoding technique requires a set of code terminating bits to be addedto each primary set of bits, the encoder comprising: input means forreceiving the primary set of bits from each set of data bits andcombining them; encoding mans for encoding the combined primary set ofbits from each set of data bits; and output means for adding a singleset of code terminating bits to the combined encoded primary sets ofbits.
 6. A packet switched network including the encoder of claim
 5. 7.The encoder of claim 5 wherein at least two sets of data bits eachinclude a header portion and a payload portion, the payload portionincluding encoded speech and the single encoded block being an RLC/MACblock.